Mixing arrangement for mixing liquid injection agent injected into exhaust gas of an internal combustion engine with the exhaust gas

Abstract

In a mixing arrangement for mixing injection agent injected into exhaust gas of an internal combustion engine with the exhaust gas, a mixing chamber has a first sub-region delimited by the upstream wall and the downstream wall, and a second sub-region delimited by the upstream wall and the downstream wall. A first inlet is provided in the upstream wall and an outlet is provided in the downstream wall so as to be assigned to the first sub-region. A second inlet opening is in the upstream wall and at least one second outlet opening is in the downstream wall so as to be assigned to the second sub-region. In the first sub-region the first inlet and the first outlet are disposed mutually offset in the first or / and the second direction. In the second sub-region the second inlet and the second outlet are disposed mutually offset in the first or / and second direction.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of German patent application no. 10 2024 135 754.1, filed Dec. 3, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] In order to reduce the proportion of pollutants in exhaust gas emitted by an internal combustion engine, it is known to inject an injection agent into the exhaust gas flowing in an exhaust gas system. For example, this injection agent can be a urea / water solution which is used in a downstream SCR catalyst to reduce the nitrogen oxide content in the exhaust gas. In another type of configuration embodiment, fuel, for example diesel, can be injected into the exhaust gas as an injection agent in order to generate reaction heat for heating the catalyst or, for example, a downstream particle filter by catalytic reaction on a downstream catalyst.BACKGROUND

[0003] When injecting an injection agent of this type, such as urea / water solution or diesel, for example, a problem can be that such injection agents are often a mixture of components with different boiling temperatures. For example, liquid components contained in diesel have boiling temperatures in the range of about 180° C. to about 430° C. This means that such an injection agent may contain components with a boiling temperature that may be higher than the exhaust gas temperature of the exhaust gas emitted by an internal combustion engine and therefore that, when injected into the exhaust gas, can be converted to a gaseous state of aggregation significantly worse than liquid components with a low boiling temperature.

[0004] Another problem when injecting an injection agent into the exhaust gas emitted by an internal combustion engine can be an insufficient or inhomogeneous mixing of the injection agent with the exhaust gas. Inhomogeneous mixing of this type may have the consequence that a part of the injection agent injected into the exhaust gas as a liquid is not converted into a gaseous state of aggregation and thus cannot be used efficiently for a subsequent catalytic reaction or oxidation reaction.SUMMARY

[0005] It is an object of the present disclosure to provide a mixing arrangement for mixing liquid reaction agent injected into exhaust gas of an internal combustion engine with the exhaust gas, by way of which an efficient transfer of the reaction agent into a gaseous state and uniform mixing of exhaust gas and reaction agent is achieved.

[0006] According to the disclosure, this object is, for example, achieved by a mixing arrangement for mixing liquid injection agent injected into exhaust gas of an internal combustion engine with the exhaust gas, including:

[0007] an exhaust gas guidance component which extends in the direction of a longitudinal axis and can be passed through by exhaust gas in an exhaust gas main flow direction, wherein formed in the exhaust gas guidance component is an exhaust gas flow volume which can be passed through by the exhaust gas substantially in the exhaust gas main flow direction,

[0008] a mixing chamber assembly having an upstream mixing chamber assembly wall which delimits a mixing chamber in the exhaust gas flow volume in the upstream direction, and a downstream mixing chamber assembly wall which delimits the mixing chamber in the exhaust gas flow volume in the downstream direction,

[0009] an injection agent dispensing unit for dispensing liquid injection agent into the mixing chamber substantially in an injection agent main dispensing direction along an injection agent dispensing line.

[0010] In the mixing arrangement constructed according to the disclosure, the mixing chamber has a first mixing chamber sub-region which is delimited by the upstream mixing chamber assembly wall and the downstream mixing chamber assembly wall, and a second mixing chamber sub-region which is delimited by the upstream mixing chamber assembly wall and the downstream mixing chamber assembly wall, wherein the first mixing chamber sub-region and the second mixing chamber sub-region are positioned next to one another in a first direction substantially transverse to the exhaust gas main flow direction and are open towards one another in a mixing chamber adjoining region, wherein the mixing chamber adjoining region in a second direction, substantially orthogonal to the first direction, is elongate substantially transversely to the exhaust gas main flow direction, wherein the injection agent dispensing unit for dispensing the injection agent is disposed in the mixing chamber adjoining region, wherein at least one first inlet opening is provided in the upstream mixing chamber assembly wall and at least one first outlet opening is provided in the downstream mixing chamber assembly wall so as to be assigned to the first mixing chamber sub-region, and at least one second inlet opening is provided in the upstream mixing chamber assembly wall and at least one second outlet opening is provided in the downstream mixing chamber assembly wall so as to be assigned to the second mixing chamber sub-region, wherein in the first mixing chamber sub-region the at least one first inlet opening and the at least one first outlet opening are disposed so as to be mutually offset in the first direction or / and in the second direction, and in the second mixing chamber sub-region the at least one second inlet opening and the at least one second outlet opening are disposed so as to be mutually offset in the first direction or / and in the second direction.

[0011] By dividing the mixing chamber into two interconnected sub-regions which are fed from the injection agent dispensing unit with the injection agent to be injected, a distribution of the injection agent injected into these two mixing chamber sub-regions or volume regions of the entire mixing chamber already takes place. In each of the mixing chamber sub-regions, a turbulent flow is generated in particular also by the positioning of the respective inlet openings and outlet openings relative to one another, which on the one hand ensures that in each of these mixing chamber sub-regions an efficient mixing of the injection agent with the proportion of the exhaust gas flow passing through the respective mixing chamber sub-region can take place, while on the other hand a comparatively long contact time of the injection agent injected into the exhaust gas with the surfaces of the mixing chamber assembly walls delimiting the various mixing chamber sub-regions is maintained. This has the effect that more time is also available for components of the liquid injection agent that transition to a gaseous state of aggregation at a lower or slower rate due to higher boiling temperatures, for example, in order to transition to a gaseous state of aggregation by absorbing heat. At the same time, the turbulent flows generated in the mixing chamber sub-regions ensure that no local accumulations of liquid injection agent are formed even under the influence of gravity, so that the formation of injection agent deposits can be prevented on the mixing chamber assembly walls, for example.

[0012] The formation of efficient turbulent flows in the mixing chamber sub-regions can be facilitated in that the first direction and the second direction are substantially orthogonal to the exhaust gas main flow direction or / and to the longitudinal axis, or / and that the injection agent main discharge direction is substantially orthogonal to the exhaust gas main flow direction or / and to the longitudinal axis, or / and substantially corresponds to the second direction.

[0013] For a substantially uniform distribution of the injected injection agent among the two mixing chamber sub-regions, it can be provided that the mixing chamber adjoining region is substantially formed by a mixing chamber adjoining opening, wherein the mixing chamber adjoining opening lies substantially in an opening plane defined by the exhaust gas main flow direction and the second direction and orthogonal to the first direction.

[0014] The injection agent dispensing line can lie substantially in the opening plane or / and be substantially orthogonal to the exhaust gas main flow direction.

[0015] In order to avoid a flow short circuit in the mixing chamber sub-regions that adversely affects the formation of turbulent flows, it is proposed that the at least one first inlet opening and the at least one first outlet opening substantially do not overlap in the second direction, or / and that the at least one second inlet opening and the at least one second outlet opening substantially do not overlap in the second direction.

[0016] Furthermore, it can be provided for this purpose that the at least one first inlet opening and the at least one first outlet opening do not overlap in the first direction at least in regions, or / and that the at least one second inlet opening and the at least one second outlet opening do not overlap in the first direction at least in regions.

[0017] For homogeneous mixing of exhaust gas and injection agent in the two mixing chamber sub-regions it can be furthermore provided that the at least one first inlet opening and the at least one second inlet opening are disposed so as to be substantially mirror-symmetrical in terms of the opening plane, or / and that the at least one first outlet opening and the at least one second outlet opening are disposed so as to be substantially mirror-symmetrical in terms of the opening plane.

[0018] When the at least one first inlet opening and the at least one second inlet opening have an entry opening spacing from the opening plane, and the at least one first outlet opening and the at least one second outlet opening have an outlet opening spacing, different from the entry opening spacing, from the opening plane, the formation of the turbulent flows in the two mixing chamber sub-regions is additionally facilitated.

[0019] In order to obtain a defined guidance of the flow along the mixing chamber assembly walls, which facilitates the efficient mixing of exhaust gas and injection agent, it can furthermore be provided that:

[0020] the upstream mixing chamber assembly wall in a wall region that delimits the first mixing chamber sub-region in the upstream direction bulges outwards in the upstream direction so as to surround a first sub-region longitudinal axis of the first mixing chamber sub-region, and in a wall region that delimits the second mixing chamber sub-region in the upstream direction bulges outwards in the upstream direction so as to surround a second sub-region longitudinal axis of the second mixing chamber sub-region,or / and

[0021] the downstream mixing chamber assembly wall in a wall region that delimits the first mixing chamber sub-region in the downstream direction bulges outwards in the downstream direction so as to surround the first sub-region longitudinal axis of the first mixing chamber sub-region, and in a wall region that delimits the second mixing chamber sub-region in the downstream direction bulges outwards in the downstream direction so as to surround the second sub-region longitudinal axis of the second mixing chamber sub-region.

[0022] For example, the configuration can be such that:

[0023] the upstream mixing chamber assembly wall and the downstream mixing chamber assembly wall bulge outwards in their respective wall region delimiting the first mixing chamber sub-region in such a manner that the first mixing chamber sub-region in terms of the first sub-region longitudinal axis has a substantially round, preferably circular or elliptic or oval cross-sectional profile,or / and

[0024] the upstream mixing chamber assembly wall and the downstream mixing chamber assembly wall bulge outwards in their respective wall region delimiting the second mixing chamber sub-region in such a manner that the second mixing chamber sub-region in terms of the second sub-region longitudinal axis has a substantially round, preferably circular or elliptic or oval cross-sectional profile.

[0025] In order to be able to provide in each case the largest possible volume for the two mixing chamber sub-regions, it is proposed that the first mixing chamber sub-region in terms of the first sub-region longitudinal axis is configured to be substantially cylindrical, and the second mixing chamber sub-region in terms of the second sub-region longitudinal axis is configured to be substantially cylindrical, or / and that the first sub-region longitudinal axis and the second sub-region longitudinal axis are disposed so as to be substantially mutually parallel.

[0026] In order to obtain a configuration that avoids the formation of deposits in a particularly efficient manner, it is proposed that the first mixing chamber sub-region is configured to be radially enlarged, preferably conically, along the first sub-region longitudinal axis, and the second mixing chamber sub-region is configured to be radially enlarged, preferably conically, along the second sub-region longitudinal axis, or / and that the first sub-region longitudinal axis and the second sub-region longitudinal axis are disposed so as to be mutually angular.

[0027] In particular, it can be provided that the at least one first inlet opening is disposed in a region of a minor radial dimension of the first mixing chamber sub-region, and the at least one first outlet opening is disposed in a region of major radial dimension of the first mixing chamber sub-region, or / and that the at least one second inlet opening is disposed in a region of minor radial dimension of the second mixing chamber sub-region, and the at least one second outlet opening is disposed in a region of major radial dimension of the second mixing chamber sub-region.

[0028] In a compact construction mode, the enlarged structure of the mixing chamber sub-regions can be efficiently integrated into the cross section of the exhaust gas guidance component when the first sub-region longitudinal axis and the second sub-region longitudinal axis are mutually angled in such a manner that a mutual spacing of the first sub-region longitudinal axis and the second sub-region longitudinal axis in a region of minor radial dimension of the first mixing chamber sub-region and the second mixing chamber sub-region is smaller than a mutual spacing of the first sub-region longitudinal axis and the second sub-region longitudinal axis in a region of major radial dimension of the first mixing chamber sub-region and the second mixing chamber sub-region.

[0029] The first sub-region longitudinal axis and the second sub-region longitudinal axis can be disposed so as to be substantially mirror-symmetrically in terms of the opening plane, regardless of whether they are mutually parallel or angular. It can furthermore be provided that the first sub-region longitudinal axis and the second sub-region longitudinal axis lie in an axis plane which is substantially orthogonal to the opening plane.

[0030] For uniform mixing of exhaust gas and injection agent in the two mixing chamber sub-regions, the first mixing chamber sub-region and the second mixing chamber sub-region can be configured to be substantially mirror-symmetrical in terms of the opening plane.

[0031] The formation of helical turbulent flows along the inner sides of the mixing chamber assembly walls can be further supported in that:

[0032] at least one flow guide element which extends about the first sub-region longitudinal axis in regions is provided on an inner side of the wall region of the upstream mixing chamber assembly wall that delimits the first mixing chamber sub-region in the upstream direction,or / and

[0033] at least one flow guide element which extends about the second sub-region longitudinal axis in regions is provided on an inner side of the wall region of the upstream mixing chamber assembly wall that delimits the second mixing chamber sub-region in the upstream direction,or / and

[0034] at least one flow guide element which extends about the first sub-region longitudinal axis in regions is provided on an inner side of the wall region of the downstream mixing chamber assembly wall that delimits the first mixing chamber sub-region in the downstream direction,or / and

[0035] at least one flow guide element which extends about the second sub-region longitudinal axis in regions is provided on an inner side of the wall region of the downstream mixing chamber assembly wall that delimits the second mixing chamber sub-region in the downstream direction.

[0036] The targeted introduction of the exhaust gas flowing towards the mixing chamber assembly into the two mixing chamber sub-regions can be facilitated in that:

[0037] a flow guide element which is to extend in the direction towards an inner side of the exhaust gas guidance component and to delimit at least one first inlet opening is provided on the wall region of the upstream mixing chamber assembly wall that delimits the first mixing chamber sub-region in the upstream direction,or / and

[0038] a flow guide element which is to extend in the direction towards the inner side of the exhaust gas guidance component and to delimit at least one second inlet opening is provided on the wall region of the upstream mixing chamber assembly wall that delimits the second mixing chamber sub-region in the upstream direction.

[0039] The present disclosure furthermore relates to an exhaust gas system for an internal combustion engine, including at least one exhaust gas treatment arrangement and upstream of at least one exhaust gas treatment arrangement a mixing arrangement constructed according to the disclosure.BRIEF DESCRIPTION OF DRAWINGS

[0040] The invention will now be described with reference to the drawings wherein:

[0041] FIG. 1 shows an exhaust gas system for an internal combustion engine in a schematic illustration;

[0042] FIG. 2 shows a longitudinal sectional view of the exhaust gas system of FIG. 1 in the region of a mixing chamber assembly thereof;

[0043] FIG. 3 shows a view of the mixing chamber assembly of FIG. 2, viewed in the direction III in FIG. 2;

[0044] FIG. 4 shows a perspective exploded illustration of a mixing arrangement;

[0045] FIG. 5 shows the mixing chamber assembly, including two mixing chamber assembly walls, of the mixing arrangement of FIG. 4, in a perspective illustration;

[0046] FIG. 6 shows a view of the mixing chamber assemblies illustrated in FIG. 5, viewed in the direction VI in FIG. 5;

[0047] FIG. 7 shows a view, corresponding to FIG. 5, of an alternative type of configuration embodiment of the mixing chamber assembly;

[0048] FIG. 8 shows a view of the mixing chamber assemblies of FIG. 7, viewed in the direction VIII in FIG. 7;

[0049] FIG. 9 shows a perspective exploded view of an alternative type of configuration embodiment of a mixing arrangement;

[0050] FIG. 10 shows a perspective view of the mixing chamber assembly, including two mixing chamber assembly walls, of the mixing arrangement of FIG. 9;

[0051] FIG. 11 shows a view of the mixing chamber assembly of FIG. 10, viewed in the direction XI in FIG. 10;

[0052] FIG. 12 shows a view of the mixing chamber assembly of FIG. 10, viewed in the direction XII in FIG. 11;

[0053] FIG. 13 shows a perspective exploded view of a further alternative type of configuration embodiment of a mixing arrangement;

[0054] FIG. 14 shows a perspective view of the mixing chamber assembly, including two mixing chamber assembly walls, of the mixing arrangement of FIG. 13;

[0055] FIG. 15 shows a view of the mixing chamber assembly of FIG. 14, viewed in the direction XV in FIG. 14; and,

[0056] FIG. 16 shows a view of the mixing chamber assembly of FIG. 14, viewed in the direction XVI in FIG. 15.DETAILED DESCRIPTION

[0057] Illustrated in FIG. 1 is a portion of an exhaust gas system, referred to generally as 10, of an internal combustion engine, for example in a vehicle. The exhaust gas system 10 includes an exhaust gas treatment arrangement 12 including, for example, a catalyst arrangement, such as SCR catalyst, to which the exhaust gas emitted by an internal combustion engine is supplied. Provided upstream of the exhaust gas treatment arrangement 12 is a mixing arrangement, referred to generally as 14, which includes, for example, a tubular exhaust gas guidance component 16. Exhaust gas A emitted by the internal combustion engine flows in an exhaust gas main flow direction HA through an exhaust gas flow volume 18 formed in the exhaust gas guidance component 16 to the mixing arrangement 14, or to a mixing chamber assembly 20 of the latter.

[0058] The mixing chamber assembly 20 includes, as can be seen in particular in FIG. 2, an upstream mixing chamber assembly wall 22 and a downstream mixing chamber assembly wall 24 which follows the upstream mixing chamber assembly wall 22 in the direction of a longitudinal axis L of the exhaust gas guidance component 16 or in the exhaust gas main flow direction HA. The two mixing chamber assembly walls 22, 24 substantially delimit a mixing chamber 26 of the mixing chamber assembly 20 in the upstream and downstream directions. An external circumferential contour of the mixing chamber assembly 20 or of the mixing chamber assembly walls 22, 24 is adapted to an internal circumferential contour of the exhaust gas guidance component 16 when viewed in the exhaust gas main flow direction HA. If the exhaust gas guidance component has a substantially circular internal circumferential contour, then the two mixing chamber assembly walls 22, 24 have a corresponding substantially circular external circumferential contour, so that the mixing chamber assembly 20 can be inserted substantially in an exact fit into the exhaust gas guidance component 16 and substantially no exhaust gas A which is to flow in the exhaust gas main flow direction HA towards the mixing chamber 20 can flow past the mixing chamber 20 in the direction of the exhaust gas treatment arrangement 12 without passing though the mixing chamber 26.

[0059] The two mixing chamber assembly walls 22, 24 are formed in such a way that two mixing chamber sub-regions 28, 30 of the mixing chamber 26 are formed, which are open towards one another in a mixing chamber adjacent region 27. So as to be assigned to the first mixing chamber sub-region 28, the upstream mixing chamber assembly wall 22 has a wall region 32 which is bulged outwards, for example in a circular manner, in the upstream direction. The wall region 32 is bulged outwards so as to surround a first sub-region longitudinal axis T1 of the first mixing chamber sub-region 28. Accordingly, so as to be assigned to the second mixing chamber sub-region 30, the upstream mixing chamber assembly wall 22 has a wall region 34 which is bulged outwards in the upstream direction and surrounds, for example in a circular manner, a second sub-region longitudinal axis T2 of the second mixing chamber sub-region 30.

[0060] So as to be assigned to the first mixing chamber sub-region 28, the downstream mixing chamber assembly wall 24 has a wall region 36 which surrounds, for example in a circular manner, the first sub-region longitudinal axis T1, and so as to be assigned to the second mixing chamber sub-region 28 has a wall region 38 which bulges outwards in the downstream direction and surrounds, for example in a circular manner, the second sub-region longitudinal axis T2.

[0061] The wall regions 32, 36 define a substantially cylindrical structure of the first mixing chamber sub-region 28 extending in the direction of the first sub-region longitudinal axis T1. Likewise, the wall regions 34, 38 define a substantially cylindrical structure of the second mixing chamber sub-region 30 extending in the direction of the second sub-region longitudinal axis T2.

[0062] Formed between a mutual adjoining region of the wall regions 32, 34 and a mutual adjoining region of the wall regions 36, 38 is a mixing chamber adjoining opening 40 of the mixing chamber adjoining region 27. The mixing chamber adjoining opening 40 extends on the one hand in the direction of the exhaust gas main flow direction HA or the longitudinal axis L of the exhaust gas guidance component 16, and on the other hand extends orthogonally thereto in a second direction R2. Also, the two sub-region longitudinal axes T1 and T2 extend substantially parallel to one another substantially in the second direction R2, thus lying in an axis plane E2 which is substantially orthogonal to the longitudinal axis L. The axis plane E2 in turn is perpendicular to an opening plane E1 which corresponds substantially to the spatial position of the mixing chamber adjoining opening 40, or defines the latter. The spatial position of the plane E1 is substantially defined by the exhaust gas main flow direction HA or the longitudinal axis L on the one hand and the second direction R2 on the other. The two sub-region longitudinal axes T1 and T2 are spaced apart from the opening plane E1 in a first direction R1. The first direction R1 is orthogonal to the second direction R2 and also to the longitudinal axis L or to the exhaust gas main flow direction HA, and thus in particular also to the opening plane E1.

[0063] In the region of the mixing chamber 26, reaction agent R to be mixed with the exhaust gas A is injected into the mixing chamber 26 in a reaction agent main dispensing direction HR along an injection agent dispensing line B by an injection agent dispensing unit 42, also referred to generally as an injector, supported on the exhaust gas guidance component 16, in the region of the mixing chamber adjoining opening 40. The injection agent dispensing line B of the injection agent R, the latter being injected substantially in the form of a cone, lies in the opening plane E1 and is substantially perpendicular to the longitudinal axis L and to the first direction R1. Thus, the injection agent main dispensing direction HR and the injection agent dispensing line B are substantially parallel to the second direction R2 and also to the sub-region longitudinal axes T1, T2, and the injection agent dispensing line B, which can substantially define a central longitudinal axis of the spray cone of the injection agent R, lies by way of the two sub-region longitudinal axes T1, T2 in the axis plane E2. In general, therefore, the injection agent dispensing line B substantially defines a longitudinal center line of a geometric structure defining the shape of the dispensed injection agent R, that is, for example, a spray cone.

[0064] By injecting the reaction agent R into the mixing chamber 26 in the region of the mixing chamber adjoining opening 40, the injection agent R substantially reaches the same proportions in the first mixing chamber sub-region 28 and in the second mixing chamber sub-region 30. In order to be able to mix these proportions of the injection agent R with the exhaust gas A, the upstream mixing chamber assembly wall 22 has a first inlet opening 44 in the wall region 32, so as to be assigned to the first mixing chamber sub-region 28. Likewise, the upstream mixing chamber assembly wall 22 has a second inlet opening 46 in the wall region 34, so as to be assigned to the second mixing chamber sub-region 30. The inlet openings 44, 46 are disposed on the upstream mixing chamber assembly wall 22 on a circumferential region which is remote from the positioning of the injection agent dispensing unit 42, or lies diametrically opposite the latter, and are configured to be substantially mirror-symmetrical in particular in terms of the opening plane E.

[0065] The two inlet openings 44, 46 are disposed at a comparatively minor inlet opening spacing from the opening plane E1, such that the exhaust gas A which is to flow substantially in the exhaust gas main flow direction HA towards the mixing chamber assembly 20 enters the mixing chamber sub-regions 28, 30 in a region that is comparatively close to the opening plane E1, at an end region of the latter that is axially spaced apart from the injection agent dispensing unit 42 in the direction of the sub-region longitudinal axes T1, T2. Since the injection agent R is also injected into this central region of the mixing chamber 26, the exhaust gas A comes into contact with the injection agent R as soon as it enters the mixing chamber sub-regions 28, 30 and begins to mix with it.

[0066] A first outlet opening 48 is formed in the wall region 36 in the downstream mixing chamber assembly wall 24, so as to be assigned to the first mixing chamber sub-region 28. Likewise, a second outlet opening 50 is formed in the wall region 38 of the downstream mixing chamber assembly wall 24, so as to be assigned to the second mixing chamber sub-region 30. As indicated in FIG. 3, the first outlet opening 48 and the second outlet opening 50 are located in a circumferential region of the downstream mixing chamber assembly wall 42 close to the injection agent dispensing unit 24 and have an outlet opening spacing from the opening plane E1 that is larger than the inlet opening spacing. It must be noted that the inlet opening spacing and the outlet opening spacing can be defined, for example, by the smallest spacing of the inlet openings 44, 46 or of the outlet openings 48, 50 from the opening plane E1, respectively. If a plurality of first or second inlet openings 44, 46, or outlet openings 48, 50 are in each case provided so as to be assigned to the first mixing chamber sub-region 28, or to the second mixing chamber sub-region 30, respectively, the minimum spacing of the inlet opening or outlet opening positioned closest to the opening plane E1 can be considered the inlet opening spacing or the outlet opening spacing, respectively.

[0067] Since the exhaust gas A flowing through the inlet openings 44, 46 into the two mixing chamber sub-regions 28, 30 can leave the mixing chamber sub-regions 28, 30 in each case only through their outlet openings 48, 50, the exhaust gas A passing through the mixing chamber sub-regions 28, 30 is forced into a turbulent flow that helically surrounds the respective sub-region longitudinal axis T1 or T2. In this turbulent flow, the exhaust gas A entrains the injection agent R injected in the region of the mixing chamber adjoining opening 40 so as to flow in the circumferential direction about the assigned sub-region longitudinal axis T1, T2 in such a way that, due to the centrifugal forces occurring, the injection agent R injected in droplet form is urged substantially radially outwards in terms of the respective sub-region longitudinal axis T1, T2. As a result, contact between the injection agent R and the inner surfaces of the mixing chamber assembly walls 22, 24 and thus the heat absorption is facilitated by the latter.

[0068] Since the exhaust gas A and conjointly therewith the injection agent R flows through the mixing chamber sub-regions 28, 30 not in a straight line, but in the helical winding turbulent flow, a comparatively long dwell time of the forming mixture G of exhaust gas A and injection agent R is guaranteed, whereby-due to the contact established or occurring with the inner surfaces of the mixing chamber assembly walls 22, 24 in the course of this flow-more heat is transmitted to the injection agent R, the evaporation or the conversion of the latter to a gaseous state of aggregation thus also being promoted.

[0069] The substantially homogeneous mixture G of exhaust gas A and gaseous injection agent R leaves the mixing chamber 26 and the mixing chamber assembly 20 through the two outlet openings 48, 50 and can then flow, for example, to carry out a catalytic reaction or an oxidation reaction, in the direction of the exhaust gas treatment arrangement 12.

[0070] Since the two mixing chamber sub-regions 28, 30, by way of their substantially cylindrical cross-sectional geometry, which is elongate in the direction of their respective sub-region longitudinal axis T1, T2, are configured to be substantially mirror-symmetrical in terms of the opening plane E1, uniform and efficient mixing of injection agent R and exhaust gas A, and a correspondingly uniform and substantially complete conversion of the injection agent, which is injected in liquid form or in the form of droplets, to a gaseous state of aggregation is achieved in the individual mixing chamber sub-regions 28, 30, this also being facilitated by the uniform distribution of the injection agent R injected in the region of the mixing chamber adjoining opening 40.

[0071] The formation of the two mutually opposing turbulent flows in the two mixing chamber sub-regions 28, 30 is facilitated by the mutually offset positioning of the respective inlet opening 44, 46 and outlet opening 48, 50 in the first direction R1 on the one hand and the offset positioning of the inlet openings 44, 46 in terms of the assigned outlet openings 48, 50 in the second direction R2. Since there is in particular a comparatively large spacing between the mutually assigned inlet openings 44, 46 and outlet openings 48, 50 in the direction of the respective sub-region longitudinal axis T1 or T2, a direct flow short circuit by way of the openings which are assigned to one another in pairs is impossible. At the same time, the helical exhaust gas flow guided through the mixing chamber sub-regions 28, 30 prevents that, when positioning the inlet openings 44, 46 in a region which is lower in the vertical direction on the inner sides of the mixing chamber assembly walls 22, 24, accumulating liquid injection agent R flows downwards and collects and forms deposits in a lower region, where the mixing chamber assembly walls 22, 24 adjoin the inner surface of the exhaust gas guidance component 16. The gravity counteracting the helical flow guidance along the respective sub-region longitudinal axis T1, T2 leads to an extension of the dwell time of the injection agent R in the region of the mixing chamber 26, so that more time is available to convert this into the gaseous state of aggregation. It can thus also be largely avoided that injection agent R which has not been vaporized or evaporated and is present in the form of droplets, is discharged from the mixing chamber 26 with the exhaust gas A.

[0072] Before various structural configuration embodiments of a mixing arrangement 14 of this type are described in detail hereunder, it should be noted that the cross-sectional geometry of the mixing chamber sub-regions could also be selected differently than is shown, for example, in FIG. 2. For example, by shaping the wall regions 32, 34, 36, 38 with a less pronounced bulge, the mixing chamber sub-regions 28, 30 which are fundamentally configured with a substantially cylindrical shape could have a substantially elliptic or optionally also an oval cross-sectional geometry in terms of the sub-region longitudinal axes T1 and T2.

[0073] FIGS. 4 to 6 show a first structural configuration embodiment of the mixing arrangement 14, which corresponds substantially to the configuration embodiment described above with reference to FIGS. 1 to 3. The two mixing chamber assembly walls 22, 24 with their wall regions 32, 34, or 36, 38 bulged outwards in the upstream or downstream direction, respectively, can be seen. In this configuration embodiment, the two inlet openings 44, 46 are displaced so far inwards towards the opening plane E1, or the mixing chamber adjoining opening 40, that the inlet openings 44, 46 transition directly into one another and thus their spacing from the opening plane E1 is equal to zero.

[0074] The two mixing chamber assembly walls 22, 24 are configured for example as formed sheet metal parts and can be connected to the inner surface of the multi-part exhaust gas guidance component 16 in the illustrated configuration embodiment by a materially integral connection, for example soldering or welding, so that a tight connection of the mixing chamber assembly walls 22, 24 on the inner surface of the exhaust gas guidance component 16, which in particular also prevents a gas leak, is ensured.

[0075] A variation of this type of configuration embodiment is illustrated in FIGS. 7 and 8. In this variation, the two inlet openings 44, 46 are displaced further outwards, that is, in the first direction R1 away from the opening plane E1 or the mixing chamber adjoining opening 40. The outlet openings 48, 50 can also be positioned as can be seen in FIGS. 4 to 6, or can be displaced further inwards, that is, towards the opening plane E1 or the mixing chamber adjoining opening 40, so that there is no overlap between the inlet openings 44, 46 on the one hand and the respective assigned outlet openings 48, 50 on the other hand, but an axial spacing not only in the direction of the respective sub-region longitudinal axis T1 or T2, but there is also a greater mutual offset in the first direction R1 so as to facilitate the formation of the turbulent flow as a result.

[0076] For further facilitating the turbulent flow, plate-type flow guide elements 52, 54 are provided, for example, on the inner surface of the downstream mixing chamber assembly wall 24, which extend substantially in the flow direction of the turbulent flow and surround respectively assigned sub-region longitudinal axis in regions, as can be seen in FIG. 7. This also efficiently prevents a direct flow short circuit from a respective inlet opening 44, 46 to the assigned outlet opening 48, 50. It must be emphasized that alternatively or additionally such flow guide elements can also be provided on the upstream mixing chamber assembly wall 22.

[0077] FIGS. 9 to 12 show an alternative type of configuration embodiment of the mixing arrangement 14, in which, as can be seen in particular in FIGS. 10 and 12, the wall regions 32, 34, which bulge in the upstream direction, of the upstream mixing chamber assembly wall 22 are more intensely curved, thus have a smaller curvature radius in the case of a circular bulge. This results in a mutual offset of the wall regions 32 and 36 and the wall regions 34 and 38, in the region lying at a spacing from the opening plane E1 or the mixing chamber adjoining opening 40, respectively.

[0078] Provided on the upstream mixing chamber assembly wall 22, on each wall region 32, 34, is a flow guide element 56, 58 which extends from the latter outwards in the direction away from the opening plane E1, the inlet opening 44, 46 being formed therebelow. For increased stability, a flow guide portion 60, 62, which extends inwards, thus in the direction towards the opening plane E1 or the mixing chamber adjoining opening 40, and which conjointly with the assigned flow guide element formed on the upstream mixing chamber assembly wall 22 delimits the respective inlet opening 44, 46, can also be formed on the respective wall region 36, 38 of the downstream mixing chamber assembly wall 24.

[0079] As can be clearly seen in FIG. 10, in this type of configuration embodiment, the mixing chamber adjoining opening 40 formed in the mixing chamber adjoining region 27 is configured to be delimited in the second direction R2, so that in the region of the mixing chamber 26, which is remote from the injection agent dispensing unit 42, the two mixing chamber sub-regions 28, 30 are separated from each other. For this purpose, a wall element can be used, for example, between the two mixing chamber sub-regions 28, 30. Alternatively, it could also be provided in this configuration embodiment that two separate components are present in the opening plane E1, one of which provides the wall region 32 and the wall region 36, and another the wall region 34 and the wall region 38. The upstream mixing chamber assembly wall 22 including the wall regions 32, 34 would thus be constructed from two parts, as would be the downstream mixing chamber assembly wall 24 including the wall regions 36, 38.

[0080] A further alternative configuration embodiment of the mixing arrangement 14 is illustrated in FIGS. 13 to 16. In this configuration embodiment, the downstream mixing chamber assembly wall 24 can again be formed, for example, as previously described with reference to FIGS. 4 to 12. This means that the wall regions 36, 38 are bulged with cylindrical geometry in terms of the respectively assigned sub-region longitudinal axis T1, T2. The upstream mixing chamber assembly wall 22 is bulged in its wall regions 32, 34 in the upstream direction in such a way that this results in a cross-sectional geometry which is conical in the direction of the respectively assigned sub-region longitudinal axes T1, T2 defined by the shaping of the upstream mixing chamber assembly wall 22. The thus defined sub-region longitudinal axes T1, T2 are thus mutually angular and lie, for example, in the axis plane E2, wherein in the lower region, that is, in the regions closer to the inlet openings 44, 46, the sub-region longitudinal axes T1, T2 have a smaller spacing and diverge from one another in the direction towards the outlet openings 48, 50.

[0081] Provided on the upstream mixing chamber assembly wall 22, in each wall region 32, 34 on the end region remote form the opening plane E1, is a flow guide element 64, 66 extending outwards, or towards the downstream mixing chamber assembly wall 24, the respective inlet opening 44 or 46, respectively, being formed therebelow.

[0082] The conical bulge of the wall regions 32, 34 with the radially enlarged cross-sectional geometry in the direction of the respective sub-region longitudinal axis T1, T2 has the consequence that in the region near the inlet openings 44, 46, due to the smaller cross-sectional geometry of the mixing chamber sub-regions 28, 30, a higher flow velocity is present, which also contributes to higher centrifugal forces due to the turbulent flow and thus to an efficient entrainment of the injection agent entering the mixing chamber sub-regions 28, 30 close to the inlet openings 44, 46. Thus, an accumulation of liquid injection agent in a lower region in the vertical direction, or a region of the mixing chamber sub-regions 28, 30 close to the inlet openings 44, 46, is efficiently counteracted.

[0083] In a variation of this type of configuration embodiment, the downstream mixing chamber assembly wall 24 in its wall regions 36, 38 could also be bulged by way of a conical geometry in terms of the respectively assigned sub-region longitudinal axis T1, T2, such that the cross-sectional size increasing in the axial direction of the sub-region longitudinal axes T1, T2 is even more pronounced.

[0084] In principle, in a mixing arrangement constructed according to the disclosure, it could also be provided that the two mixing chamber sub-regions 28, 30 are positioned in terms of the longitudinal axis L or the exhaust gas main flow direction HA in such a way that their sub-region longitudinal axes T1, T2 are angled in terms of the axis plane E2 and, for example, are inclined downstream or upstream in the direction of the inlet openings 44, 46 to the outlet openings 48, 50.

[0085] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A mixing arrangement for mixing injection agent injected into exhaust gas of an internal combustion engine with the exhaust gas, the mixing arrangement comprising:an exhaust gas guidance component which extends in a direction of a longitudinal axis and is configured to be passed through by exhaust gas in an exhaust gas main flow direction, wherein an exhaust gas flow volume is formed in the exhaust gas guidance component and said exhaust gas flow volume is configured to be passed through by the exhaust gas in the exhaust gas main flow direction;a mixing chamber assembly having an upstream mixing chamber assembly wall which delimits a mixing chamber in said exhaust gas flow volume in the upstream direction, and a downstream mixing chamber assembly wall which delimits said mixing chamber in said exhaust gas flow volume in the downstream direction;an injection agent dispensing unit for dispensing liquid injection agent into the mixing chamber in an injection agent main dispensing direction along an injection agent dispensing line;said mixing chamber having a first mixing chamber sub-region delimited by said upstream mixing chamber assembly wall and said downstream mixing chamber assembly wall;said mixing chamber further having a second mixing chamber sub-region delimited by said upstream mixing chamber assembly wall and said downstream mixing chamber assembly wall;said first mixing chamber sub-region and said second mixing chamber sub-region being positioned mutually adjacent in a first direction transverse to the exhaust gas main flow direction and being open towards one another in a mixing chamber adjoining region, wherein said mixing chamber adjoining region in a second direction, orthogonal to the first direction, is elongate transversely to the exhaust gas main flow direction;said injection agent dispensing unit being disposed in the mixing chamber adjoining region;said upstream mixing chamber assembly wall defining at least one first inlet opening;wherein said upstream mixing chamber assembly wall defines at least one first inlet opening and said downstream mixing chamber assembly wall defines at least one first outlet opening so as to be assigned to said first mixing chamber sub-region;wherein said upstream mixing chamber assembly wall defines at least one second inlet opening and said downstream mixing chamber assembly wall defines at least one second outlet opening so as to be assigned to said second mixing chamber sub-region;wherein in said first mixing chamber sub-region said at least one first inlet opening and said at least one first outlet opening are disposed so as to be mutually offset in at least one of the first direction and the second direction; and,wherein in said second mixing chamber sub-region said at least one second inlet opening and said at least one second outlet opening are disposed so as to be mutually offset in at least one of the first direction and the second direction.

2. The mixing arrangement of claim 1, wherein at least one of:the first direction and the second direction are orthogonal to at least one of the exhaust gas main flow direction and the longitudinal axis; and,the injection agent main dispensing direction is orthogonal to at least one of the exhaust gas main flow direction and the longitudinal axis, or / and corresponds to the second direction.

3. The mixing arrangement of claim 1, wherein said mixing chamber adjoining region is formed by a mixing chamber adjoining opening; and, said mixing chamber adjoining opening lies in an opening plane defined by the exhaust gas main flow direction and the second direction and orthogonal to the first direction.

4. The mixing arrangement of claim 3, wherein at least one of:the injection agent dispensing line lies in the opening plane; and,the injection agent dispensing line is orthogonal to the exhaust gas main flow direction.

5. The mixing arrangement of claim 1, wherein at least one of:said at least one first inlet opening and said at least one first outlet opening do not overlap in the second direction; and,said at least one second inlet opening and said at least one second outlet opening do not overlap in the second direction.

6. The mixing arrangement of claim 1, wherein at least one of:said at least one first inlet opening and said at least one first outlet opening do not overlap in the first direction at least in regions; and,said at least one second inlet opening and said at least one second outlet opening do not overlap in the first direction at least in regions.

7. The mixing arrangement of claim 3, wherein at least one of:said at least one first inlet opening and said at least one second inlet opening are disposed so as to be mirror-symmetrical in terms of the opening plane; and,said at least one first outlet opening and said at least one second outlet opening are disposed so as to be mirror-symmetrical in terms of the opening plane.

8. The mixing arrangement of claim 3, wherein said at least one first inlet opening and said at least one second inlet opening have an inlet opening spacing from the opening plane; and, said at least one first outlet opening and said at least one second outlet opening have an outlet opening spacing, different from the inlet opening spacing, from the opening plane.

9. The mixing arrangement of claim 1, wherein at least one of:said upstream mixing chamber assembly wall in a first wall region that delimits said first mixing chamber sub-region in the upstream direction bulges outwards in the upstream direction so as to surround a first sub-region longitudinal axis of said first mixing chamber sub-region, and in a second wall region that delimits said second mixing chamber sub-region in the upstream direction bulges outwards in the upstream direction so as to surround a second sub-region longitudinal axis of said second mixing chamber sub-region; and,said downstream mixing chamber assembly wall in a third wall region that delimits said first mixing chamber sub-region in the downstream direction bulges outwards in the downstream direction so as to surround the first sub-region longitudinal axis of said first mixing chamber sub-region, and in a fourth wall region that delimits said second mixing chamber sub-region in the downstream direction bulges outwards in the downstream direction so as to surround the second sub-region longitudinal axis of said second mixing chamber sub-region.

10. The mixing arrangement of claim 9, wherein at least one of:said upstream mixing chamber assembly wall and said downstream mixing chamber assembly wall bulge outwards in corresponding ones of said first wall region and said third wall region delimiting the first mixing chamber sub-region such that said first mixing chamber sub-region in terms of the first sub-region longitudinal axis has at least one of a round, circular, elliptic, and oval cross-sectional profile; and,said upstream mixing chamber assembly wall and said downstream mixing chamber assembly wall bulge outwards in corresponding ones of said second wall region and said fourth wall region delimiting said second mixing chamber sub-region such that said second mixing chamber sub-region in terms of said second sub-region longitudinal axis has at least one of a round, circular, elliptic, and oval cross-sectional profile.

11. The mixing arrangement of claim 9, wherein at least one of:said first mixing chamber sub-region in terms of the first sub-region longitudinal axis is cylindrical, and said second mixing chamber sub-region in terms of the second sub-region longitudinal axis is cylindrical; and,,the first sub-region longitudinal axis and the second sub-region longitudinal axis are disposed so as to be mutually parallel.

12. The mixing arrangement of claim 9, wherein at least one of:said first mixing chamber sub-region is configured to be radially enlarged along the first sub-region longitudinal axis, and the second mixing chamber sub-region is configured to be radially enlarged along the second sub-region longitudinal axis; and,the first sub-region longitudinal axis and the second sub-region longitudinal axis are disposed so as to be mutually angular.

13. The mixing arrangement of claim 9, wherein at least one of:said first mixing chamber sub-region is configured to be radially enlarged conically along the first sub-region longitudinal axis, and the second mixing chamber sub-region is configured to be radially enlarged conically along the second sub-region longitudinal axis; and,the first sub-region longitudinal axis and the second sub-region longitudinal axis are disposed so as to be mutually angular.

14. The mixing arrangement of claim 12, wherein at least one of:said at least one first inlet opening is disposed in a region of a minor radial dimension of said first mixing chamber sub-region, and said at least one first outlet opening is disposed in a first region of major radial dimension of said first mixing chamber sub-region; and,said at least one second inlet opening is disposed in a region of minor radial dimension of said second mixing chamber sub-region, and said at least one second outlet opening is disposed in a second region of major radial dimension of said second mixing chamber sub-region.

15. The mixing arrangement of claim 12, wherein the first sub-region longitudinal axis and the second sub-region longitudinal axis are mutually angled such that a mutual spacing of the first sub-region longitudinal axis and the second sub-region longitudinal axis in a region of minor radial dimension of the first mixing chamber sub-region and said second mixing chamber sub-region is smaller than a mutual spacing of the first sub-region longitudinal axis and the second sub-region longitudinal axis in the region of major radial dimension of said first mixing chamber sub-region and said second mixing chamber sub-region.

16. The mixing arrangement of claim 9, wherein said mixing chamber adjoining region is formed by a mixing chamber adjoining opening; and, said mixing chamber adjoining opening lies in an opening plane defined by the exhaust gas main flow direction and the second direction and orthogonal to the first direction;wherein at least one of:the first sub-region longitudinal axis and the second sub-region longitudinal axis are disposed so as to be mirror-symmetrical in terms of the opening plane; and,the first sub-region longitudinal axis and the second sub-region longitudinal axis lie in an axis plane which is orthogonal to the opening plane.

17. The mixing arrangement of claim 3, wherein said first mixing chamber sub-region and said second mixing chamber sub-region are mirror-symmetrical in terms of the opening plane.

18. The mixing arrangement of claim 9 further comprising at least one of:at least one first flow guide element which extends about the first sub-region longitudinal axis in regions provided on an inner side of said first wall region of said upstream mixing chamber assembly wall that delimits said first mixing chamber sub-region in the upstream direction;at least one second flow guide element which extends about said second sub-region longitudinal axis in regions provided on an inner side of said second wall region of said upstream mixing chamber assembly wall that delimits said second mixing chamber sub-region in the upstream direction;at least one flow guide element which extends about the first sub-region longitudinal axis in regions provided on an inner side of said third wall region of said downstream mixing chamber assembly wall that delimits said first mixing chamber sub-region in the downstream direction; and,at least one fourth flow guide element which extends about the second sub-region longitudinal axis in regions provided on an inner side of said fourth wall region of said downstream mixing chamber assembly wall that delimits said second mixing chamber sub-region in the downstream direction.

19. The mixing arrangement of claim 9 further comprising at least one of:a first flow guide element extending in a direction towards an inner side of said exhaust gas guidance component and delimiting said at least one first inlet opening provided on said first wall region of said upstream mixing chamber assembly wall that delimits said first mixing chamber sub-region in the upstream direction; and,a second flow guide element extending in the direction towards said inner side of said exhaust gas guidance component and delimiting said at least one second inlet opening provided on said second wall region of said upstream mixing chamber assembly wall that delimits said second mixing chamber sub-region in the upstream direction.

20. An exhaust gas system for an internal combustion engine, comprising:an exhaust gas treatment arrangement;a mixing arrangement arranged upstream of said exhaust gas treatment arrangement;said mixing arrangement having an exhaust gas guidance component which extends in a direction of a longitudinal axis and is configured to be passed through by exhaust gas in an exhaust gas main flow direction, wherein an exhaust gas flow volume is formed in the exhaust gas guidance component and said exhaust gas flow volume is configured to be passed through by the exhaust gas in the exhaust gas main flow direction;said mixing arrangement further having a mixing chamber assembly having an upstream mixing chamber assembly wall which delimits a mixing chamber in said exhaust gas flow volume in the upstream direction, and a downstream mixing chamber assembly wall which delimits said mixing chamber in said exhaust gas flow volume in the downstream direction;said mixing arrangement having an injection agent dispensing unit for dispensing liquid injection agent into the mixing chamber in an injection agent main dispensing direction along an injection agent dispensing line;said mixing chamber having a first mixing chamber sub-region delimited by said upstream mixing chamber assembly wall and said downstream mixing chamber assembly wall;said mixing chamber further having a second mixing chamber sub-region delimited by said upstream mixing chamber assembly wall and said downstream mixing chamber assembly wall;said first mixing chamber sub-region and said second mixing chamber sub-region being positioned mutually adjacent in a first direction transverse to the exhaust gas main flow direction and being open towards one another in a mixing chamber adjoining region, wherein said mixing chamber adjoining region in a second direction, orthogonal to the first direction, is elongate transversely to the exhaust gas main flow direction;said injection agent dispensing unit being disposed in the mixing chamber adjoining region;said upstream mixing chamber assembly wall defining at least one first inlet opening;wherein said upstream mixing chamber assembly wall defines at least one first inlet opening and said downstream mixing chamber assembly wall defines at least one first outlet opening so as to be assigned to said first mixing chamber sub-region;wherein said upstream mixing chamber assembly wall defines at least one second inlet opening and said downstream mixing chamber assembly wall defines at least one second outlet opening so as to be assigned to said second mixing chamber sub-region;wherein in said first mixing chamber sub-region said at least one first inlet opening and said at least one first outlet opening are disposed so as to be mutually offset in at least one of the first direction and the second direction; and,wherein in said second mixing chamber sub-region said at least one second inlet opening and said at least one second outlet opening are disposed so as to be mutually offset in at least one of the first direction and the second direction.

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